Yunseok Seo

Holographic hadrons in a confining finite density medium

We study a sector of the hadron spectrum in the presence of finite baryon density. We use a non-supersymmetric gravity dual to a confining gauge theory which exhibits a running dilaton. The interaction of mesons with the finite density medium is encoded in the dual theory by a force balancing between flavor D7-branes and a baryon vertex provided by a wrapped D5-brane. When the current quark mass mq is sufficiently large, the meson mass reduces, exhibiting an interesting spectral flow as we increase the baryon density while it has a more complicated behaviour for very small mq.

Holographic D instanton liquid and chiral transition

We study the phase diagram of black D3 geometry with uniformly distributed D-instanton charge using the probe D7 brane. In the presence of uniform D-instanton charges, quarks can be confined, although gluons are not, because baryon vertices are allowed due to the net repulsive force on the on the probe D-branes. Since there is no scale in the geometry itself apart from the horizon size, there is no Hawking-Page transition. As a consequence, the D7 brane embedding can encode the effect of the finite temperature as well as finite baryon density even for low temperature. The probe D-brane embedding, however, undergoes a phase transition which can be interpreted as a chiral transition as we change temperature and density. We studied such phase transitions and calculated the constituent quark mass, chiral condensation, and the binding energy of baryons as function of the density. The baryon vertex melting is identified as the quark deconfinement. We draw the phase diagram according to these transitions.

Nuclear matter to strange matter transition in holographic QCD

We construct a simple holographic QCD model to study nuclear matter to strange matter transition. The interaction of dense medium and hadrons is taken care of by imposing the force balancing condition for stable D4/D6/D6 configuration. By considering the intermediate and light flavor branes interacting with baryon vertex, which is homogeneously distributed along R3 space, and by requesting the energy minimization, we find that there is a well defined transition density as a function of current quark mass. We also find that as density goes up very high, intermediate (or heavy) and light quarks populate equally. Since these are expected from the Pauli exclusion principle, we speculate that the effect of the Pauli exclusion principle in the field theory is realized by the repulsive force between the U(1) charges and the dynamics of D-branes.

The dropping of in-medium hadron mass in holographic QCD

We study the baryon density dependence of the vector meson spectrum using the D4/D6 system together with the compact D4 baryon vertex. We find that the vector meson mass decreases almost linearly in density at low density for small quark mass, but saturates to a finite non-zero value for large density. We also compute the density dependence of the η′ mass and the η′ velocity. We find that in medium, our model is consistent with the GMOR relation up to a few times the normal nuclear density. We compare our hQCD predictions with predictions made based on hidden local gauge theory that is constructed to model QCD.

Holographic model with a Neveu-Schwarz-Neveu-Schwarz field

We consider a holographic model constructed through using the D4/D8-

Symmetry energy and universality classes of holographic QCD

\overline{\rm D8}

QCD phase transitions with dense matter in holographic QCD

brane configuration with a background field. We study some properties of the effective field theory in this intersecting brane construction, and calculate the effects of this NS-NS background field on some underlying dynamics. We also discuss some other general brane configurations.

Holographic meson mass in asymmetric dense matter

A bstractWe study nuclear symmetry energy of dense matter using holographic QCD. We calculate it in a various holographic QCD models and show that the scaling index of the symmetry energy in dense medium is almost invariant under the smooth deformation of the metric as well as the embedding shape of the probe brane. We find that the scaling index depends only on the dimensionality of the branes and space-time. Therefore the scaling index of the symmetry energy characterizes the universality classes of holographic QCD models. We suggest that the scaling index might be also related to the non-fermi liquid behavior of the interacting nucleons.

Note on a noncritical holographic model with a magnetic field

We study the phase diagram of a holographic QCD using the probe D7 brane in the black hole geometry comes from the D3/D-instanton system. Due to the instanton charge, quark anti-quark potential has quasi-confining behavior and the baryon vertex can exit outside the horizon. We can find D7 brane embeddingswith the finite baryon density and the finite chiral condensation as well as an embedding where only quarks are possible but the chiral condensation can be zero or non-zero. We study the phase transition and the phase diagram between these phases.